“It’s going to get real loud, real fast!” The public address announcer shouted that warning to a packed Action Sports Arena inside the Orange County Fair, where county police officers and firefighters were about to smash each other in the Motorhome Madness Demolition Derby on Friday night. After 30 minutes of bashing and crashing, the RV commandeered by Tustin Police Chief Stu Greenberg was the only one of the RVs in the derby still able to move, albeit barely. And as any fan of demolition derbies knows, the last man standing is the winner. “I expected to be out first,”…